A spring is typically made of a wire formed helically into coils, and the spring has an elastic property defined as the spring constant K. In a compression spring, the free length of the spring is the length of the spring in a relaxed state, or uncompressed, that is the spring with no external compression force applied. A maximum compression of the spring is referred to as the solid height of the spring. The solid height is the length of the compressed spring under sufficient load to bring all coils into contact with adjacent coils. However, a spring has a maximum elasticity point that is less than its solid height. If the spring is compressed beyond its maximum elasticity point, then the spring begins to lose its elastic properties. Therefore, in order to maintain the spring constant K, the spring should not be compressed beyond its maximum elasticity point. Springs are used in many applications, including the use as drivers for plungers. It is a frequent design consideration for the driver to be as small as possible.